In a wireless communications system, a hybrid automatic repeat request (HARQ) technology is an important technology which can improve data link reliability.
Low-density parity-check (LDPC) code is a type of linear block code that has a sparse parity-check matrix and is featured by a flexible structure and low decoding complexity. Due to use of an iteration decoding algorithm of partial parallelism, the LDPC code has a higher throughput rate than conventional Turbo code. The LDPC code is considered as next-generation error correcting code for a communications system and can be used to improve reliability and power utilization of channel transmission, and can be widely applied to space communication, fiber optic communications, a personal communications system, an asymmetric digital subscriber line (ADSL), a magnetic recording device, and the like. Currently, in the 5th generation (5G) mobile communication, the LDPC code has been considered to be used as one of channel coding schemes.
To support different code lengths and code rates, a communications device performs rate matching after channel coding to adjust a code rate of a coded block, and obtains a bit sequence that needs to be sent, to match a decoding code rate. The communications device may further perform bit puncturing on an LDPC coded block during rate matching, to increase the code rate; or the communications device performs bit repetition on an LDPC coded block during rate matching, to decrease the code rate.
During the rate matching, the communications device on a transmit end selects a bit sequence that needs to be sent, and sends the bit sequence to a communications device on a receive end after performing processes such as interleaving and mapping etc. The communications device on the receive end combines soft values of the bit sequence with stored soft value bits (soft channel bit) and performs decoding, to obtain the code block.
In the prior art, when using an existing rate matching method, the communications device has poor HARQ performance.